1. Field of the Invention
The present invention relates generally to vision augmentation for GNSS/INS receivers and more particularly to vision augmentation using partially occluded images for GNSS/INS receivers.
2. Background Information
Vehicle may utilize some form of satellite navigation system, such as a GNSS system. The GNSS system may be paired with an inertial navigation system (INS) for improved accuracy. The combined GNSS/INS system provides current location and navigation information that may be utilized by the driver for accurate navigation. The INS system may aid in navigation when the GNSS system loses accuracy which may occur when, for example multipath situations occur. A multipath situation occurs when, e.g., signals transmitted from the GNSS satellites are reflected by local terrain and/or buildings, thereby resulting in a plurality of signals being received by the GNSS receiver. Due to the plurality of signals being received, each of which may be phase shifted and/or time delayed, the GNSS receiver may not be able to accurately detect its location.
The INS system may be utilized to improve accuracy of navigation information in multipath situations. Further, a vision system may be implemented to obtain additional location information to be used to improve INS solutions as to current location and velocity. However, when analyzing a sequence of images that are being used for navigation by the vision system, if one image becomes occluded or otherwise cannot be used to identify sufficient tie points, the solution for the entire sequence of image may become mathematically unstable. This may result in navigation updates not being able to be provided to the INS system. Generally, for every image pair there are six unknowns that need to be resolved, thereby requiring six image observations (i.e., tie points) within the image. In an exemplary sequence of 10 images, this results in 54 unknowns. To solve for such a system, every image must track six tie points. However, it should be noted that acquired images may be occluded for any of a plurality of reasons. For example, if a vision system is located on an automobile, a large truck may pass in front of the vehicle, thereby preventing the vision system from obtaining the required tie points in a plurality of sequentially acquired images. Similarly, mountains or other geographic features may result in the inability to obtain the required observations. In such situations, the vision system loses the ability to provide updates to the INS system. As such, the INS system may lose some degree of accuracy with a concomitant loss of accuracy overall navigation system when combined with the GNSS navigation information.